Closed-loop refrigeration systems conventionally employ a compressor that is meant to draw in gaseous refrigerant at relatively low pressure and discharge hot refrigerant at relatively high pressure. The hot refrigerant condenses into liquid as it is cooled in a condenser. A small orifice or valve divides the system into high and low-pressure sides. The liquid on the high-pressure side passes through the orifice or valve and turns into a gas in the evaporator as it picks up heat. (Some systems operate in “transcritical” mode, in that the hot refrigerant is merely cooled in a high side heat exchanger, now termed a “gas cooler”, and turns to gas plus liquid as it passes through the expansion device.) At low heat loads, it is not desirable or possible to evaporate all the liquid in the evaporator. However, excess liquid refrigerant entering the compressor (known as “slugging”) causes system efficiency loss and can cause damage to the compressor. Hence it is standard practice to include a reservoir between the evaporator and the compressor to separate and store the excess liquid. It is also a reservoir for excess refrigerant, which is typically added to the system during manufacture to compensate for unavoidable leakage during the working life of the system. This reservoir is called a suction line accumulator, or simply an accumulator.
An accumulator is typically a metal can, welded together, and often has fittings attached for a switch, transducer and/or charge port. One or more inlet tubes and an outlet tube pierce the top, sides, or occasionally the bottom, or attach to fittings provided for that purpose. The refrigerant flowing into a typical accumulator will impinge upon a deflector or baffle intended to reduce the likelihood of liquid flowing out the exit, generally by removing kinetic energy from the liquid so it settles quietly into the reservoir area without churning or splashing. Some patents describe accumulators without deflectors (such as U.S. Pat. Nos. 5,179,844 and 5,471,854). However, the lack of a deflector reduces effective reservoir volume and reduces efficiency by allowing churning and splashing that returns unnecessary liquid to the compressor—that is, by allowing liquid carryover. Moreover, even when deflectors have been used in the past, the deflectors have contributed to turbulence, when the incoming fluid rebounds off the deflectors.
A consequence of using a suction line accumulator is that compressor oil can become trapped within it. Compressor oil is circulated with the refrigerant in most systems in current usage. Even if a separator is used, a small amount of oil escapes into the system. This oil will find its way into the accumulator, and while liquid refrigerant may be expected to evaporate and return to circulation as needed, the oil does not evaporate. Some means must be provided to return this oil to circulation. A known practice is to use a J-shaped outlet tube to carry the exiting gaseous refrigerant from the top of the accumulator down to the bottom and then back up to the outlet from the accumulator. A carefully sized orifice at the bottom of this “J-tube” (sometimes also referred to as a “U-tube”) entrains the oil from the bottom of the liquid area into the stream of exiting gas. A recent development in accumulator design is to incorporate a plastic liner in the accumulator to assist with the oil pick up function (as shown in U.S. Pat. Nos. 6,612,128 and 6,463,757).
While previous deflector and accumulator designs have considered configurations to help prevent liquid refrigerant from exiting the accumulator, the previous designs do not appear to have addressed deflector design to improve the separation of liquid from vapour (while maintaining little liquid carryover).
Deflectors within accumulators have typically been designed to act only as shields to protect an outlet tube (or a J-tube or a gas flow tube (all of which may be referred to as a conduit primarily for gas)) from stray liquid refrigerant. It would be desirable to have a deflector that improves the separation of liquid and gas, while also protecting the outlet (or gas flow tube) from liquid refrigerant.